Extinction length

Other advantages for diffraction at synchrotron sources include the minimization of systematic errors, which limit the accuracy with which crystallographic models can be refined. Both extinction and absorption are strongly dependent on crystal size and wavelength with the primary extinction characterized by an extinction length ... 

Inside the totally reflecting range, is real and the wave is strongly attenuated. In X-ray diffraction theory, this phenomenon is referred to as primary extinction. The extinction length, defined as the distance over which the amplitude of the incident wave decreases to /e of its value, is P/Q at the centre of the reflexion band. 

The quantity e is called the absorption coefficient or extinction coefficient, more completely the molar decadic absorption coefficient it is a characteristic of the substance and the wavelength and to a lesser extent the solvent and temperature. It is coimnon to take path length in centimetres and concentration in moles per... 

The intensity of a spectral absorption band at a given wave length is expressed in terms of absorption or extinction coefficients, dehned on the basis of the Beer-Lambert law. The latter states that the fraction of incident light absorbed is proportional to the number of molecules in the light path, i.e., to the concentration (c) and the path length (1). The law may be expressed mathematically as ... 

The electronic transitions which produce spectra in the visible and ultraviolet are accompanied by vibrational and rotational transitions. In the condensed state, however, rotation is hindered by solvent molecules, and stray electrical fields affect the vibrational frequencies. For these reasons, electronic bands are very broad. An electronic band is characterised by the wave length and moleculai extinction coefficient at the position of maximum intensity (Xma,. and emai.). 

Ai), /is the path length in centimeters of the absorber, and S is the molar extinction coefficient having units cm . The absorbance is defined as... 

Since the arc extinction technique is highly effective and quick and occurs when the arcing contact is still moving, arc length and hence contact travel, can be reduced as can the arc energy and the excessive heating as well as erosion of the arcing contacts. An extended contact life can thus be achieved by this technique. 

A transmissometer is similar to a telephotometer except that the target is a known light source. If we know the characteristics of the source, the average extinction coefficient over the path of the beam may be calculated. Transmissometers are not very portable in terms of looking at a scene from several directions. They are also very sensitive to atmospheric turbulence, which limits the length of the light beam. 

Extinction Coefficient a measure of the ability of particles or gases to absorb and scatter photons from a beam of light a number that is proportional to the number of photons removed from the sight path per unit length. See absorption. Extinction Cross Section the amount of light scattered and absorbed by a particle divided by its physical cross section. 

Transmissometer an instrument that measures the amount of light extinction over a fixed, specified path length. 

The specific absorption (or extinction) coefficient Es (sometimes termed absorbancy index) may be defined as the absorption per unit thickness (path length) and unit concentration. 

In equation (5), T is the turhidity, O.D. is the optical density measvired from the photometer, N is the number density of parti-cles, X is the optical path length and Rext extinction... 

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